1. Field of Invention
The present invention relates to a projector for projecting and displaying an image with the use of a liquid crystal panel.
2. Description of Related Art
In a projector using a liquid crystal panel, light emitted from an illuminating system is modulated according to image information (image signals) with the use of a liquid crystal light valve including a liquid crystal panel, and the modulated image light (light representing an image) is projected onto a screen with the use of a projection lens, thereby achieving image display.
The liquid crystal light valve has the property of changing contrast according to an incidence angle of light. Therefore, in a conventional projector, the contrast of an image projected onto the screen is totally decreased according to an angle of incident light (hereinafter, this phenomenon is referred to as xe2x80x9cincidence angle dependency of contrastxe2x80x9d). When the incidence angle of light is in one direction, this phenomenon may be resolved by adjusting the incidence angle of light to a direction in which contrast becomes highest. However, it is almost impossible to obtain light in one direction from a light source device, and various optical elements, such as lenses or mirrors, are disposed between the light source device and the liquid crystal light valve in the projector. Therefore, it is very difficult to adjust the angle of light incident on the liquid crystal light valve in one direction. In addition, in a recent projector, a so-called integrator system is used in order to apply light having a uniform illumination distribution onto the liquid crystal light valve. Since this integrator system is an optical system which divides a light emitted from a light source device into a plurality of partial light to form a plurality of spatially separated pseudo light sources, and superimposes the light sources on a light incidence surface of the liquid crystal light valve to thereby illuminate the light valves, light is applied onto the liquid crystal light valve from various directions. In general, illuminance of illumination light is uniformly distributed as the number of pseudo light source images is increased. However, the more the number of the pseudo light source images is increased, the more the number of directions of light incident on the liquid crystal light valve is increased. Therefore, according to the projector using the integrator system, it is particularly difficult to increase the contrast of the overall projection screen.
This invention is made to solve the above-described problems in the conventional art, and an object is to provide a technique capable of increasing contrast of a projected and displayed image in a projector.
In order to solve at least a part of the above-described problems, according to a first apparatus of the present invention, there is provided a projector including:
an illuminating system that emits illumination light;
a liquid crystal light valve that modulates light from the illuminating system according to image information; and
a projection system that projects image light formed on a light emission surface of the liquid crystal light valve;
wherein the liquid crystal light valve includes:
a liquid crystal panel;
a first polarizer disposed on the side of the light incidence surface of the liquid crystal panel;
a second polarizer disposed on the side of the light emission surface of the liquid crystal panel;
a first compensating plate disposed between the liquid crystal panel and the first polarizer; and
a second optical compensating plate disposed between the liquid crystal panel and the second polarizer.
In the projector of the present invention, the liquid crystal light valve includes a compensating plate on the side of the light incidence surface and on the side of the light emission surface of the liquid crystal panel. This will reduce the aforementioned incidence angle dependency of contrast, whereby it is possible to increase contrast of an image projected and displayed by the projection system.
According to a second apparatus of the present invention, there is provided a projector that projects and displays a color image, including:
an illuminating system that emits illumination light;
a color separation system that separates the illumination light emitted from the illumination system into first to third color lights having three color components;
first to third liquid crystal light valves that modulate first to third color lights separated by the color separation system according to image information;
a color synthesizing section that synthesizes image lights formed on light emission surfaces of the first to third liquid crystal valves; and
a projection system that projects synthesized light emitted from the color synthesizing section;
wherein each of the first to third liquid crystal light valves includes:
a liquid crystal panel;
a first polarizer disposed on the side of the light incidence surface of the liquid crystal panel;
a second polarizer disposed on the side of the light emission surface of the liquid crystal panel;
a first compensating plate disposed between the liquid crystal panel and the first polarizer; and a second compensating plate disposed between the liquid crystal panel and the second polarizer.
In the second projector, incidence angle dependency of contrast can also be reduced in the same manner as the first projector, so that the contrast of a color image projected and displayed by the projection system can be increased.
According to a third apparatus of the present invention, there is provided a projector, including:
an illuminating system that emits illumination light;
a liquid crystal light valve that modulates light from the illuminating system according to image information; and
a projection system that projects image light formed on a light emission surface of the liquid crystal light valve;
wherein the liquid crystal light valve includes:
a liquid crystal panel;
a first polarizer disposed on the side of the light incidence surface of the liquid crystal panel;
a second polarizer disposed on the side of the light emission surface of the liquid crystal panel; and
a first and a second compensating plates disposed between the liquid crystal panel and the first polarizer or between the liquid crystal panel and the second polarizer.
In the third projector, a first and a second compensating plate are disposed between the liquid crystal panel and the first polarizer or between the liquid crystal panel and the second polarizer. This will reduce the aforementioned incidence angle dependency of contrast in the same manner as the first projector, so that the contrast of an image projected and displayed by the projection system can be increased.
According to a fourth apparatus of the present invention, there is provided a projector that projects and displays a color image, including:
an illuminating system that emits illumination light;
a color separation system that separates the illumination light emitted from the illumination system into first to third color lights having three color components;
first to third liquid crystal light valves that modulate first to third color lights separated by the color separation system according to image information;
a color synthesizing section that synthesizes image lights formed on light emission surfaces of the first to third liquid crystal valves; and
a projection system that projects synthesized light emitted from the color synthesizing section;
wherein each of the first to third liquid crystal light valves includes:
a liquid crystal panel;
a first polarizer disposed on the side of the light incidence surface of the liquid crystal panel;
a second polarizer disposed on the side of the light emission surface of the liquid crystal panel; and
a first and a second compensating plate disposed between the liquid crystal panel and the first polarizer or between the liquid crystal panel and the second polarizer.
In the second projector, incidence angle dependency of contrast can also be reduced in the same manner as the third projector, so that the contrast of a color image projected and displayed by the projection system can be increased.
In the above-described projector, the illuminating system may include:
a light source device that emits a nearly parallel light;
a light dividing element that divides the light emitted from the light source device into a plurality of partial light; and
a superimposing lens that superimposes and illuminates the plurality of partial light emitted from the light dividing element on the light incidence surface of the liquid crystal light valve.
A so-called integrator system which divides a light emitted from the light source device into a plurality of partial light, and superimposes the partial light on the light incidence surface of the liquid crystal light valve is an optical system for applying light from a plurality of pseudo light sources to the light valve, so that light will be applied to the liquid crystal light valve from plural directions. Since the first and second compensating plates are used in the projector of the present invention, incidence angle dependency of contrast can be reduced even if light enters the liquid crystal light valve from plural directions as described above. Consequently, it is possible to increase contrast of the image projected and displayed by the projection system. When the integrator system is used, light enters from various directions, and contrast cannot be increased by a conventional method such that the incidence angle of light is adjusted to a direction in which contrast becomes highest, so that the use of the present invention is particularly highly effective.
In the above-described projector, the liquid crystal panel may be in a TN mode.
When a liquid crystal panel in the TN mode is utilized as the liquid crystal light valve, contrast tends to have incidence angle dependency. Therefore, the present invention is particularly highly effective when the liquid crystal panel in the TN mode is used.
In the above-described projector, the compensating plate preferably includes a polymer layer in which the angle of inclination of an optical axis varies in the direction of the thickness.
A liquid crystal layer of the liquid crystal light valve takes a complicated structure in which the inclination of liquid crystal molecules varies in the direction of the thickness when the ON-drive voltage is applied thereto. Unless the inclination of the liquid crystal molecules is constant, light enters each of the liquid crystal molecules from different directions. This means that leakage of light occurs in black display when a liquid crystal light valve in a normally white mode, that represents black in a state of application of the ON-drive voltage, is used. According to the compensating plate including a polymer layer in which the angle of the optical axis is uniformly inclined, the complicated inclination of the liquid crystal molecules cannot be completely compensated, and there is a possibility that increasing effects of contrast is reduced. On the other hand, if the compensating plate including a polymer layer in which the angle of inclination of the optical axis varies in the direction of the thickness is used, it is possible to compensate the influence of complicated inclination of the liquid crystal molecules, whereby good contrast can be obtained.
The above-described projector may further include a circuit board for supplying signals to the liquid crystal panel.
The above-described projector may further include a power source for supplying electric power to the liquid crystal panel.